German energy agency, dena's, Efficient Homes project is tapping into substantial energy savings through the retrofits of existing buildings.

As energy prices on the world market rise and the debate on how to address climate change intensifies, energy-efficient home retrofits have become a vital issue in Germany. The residential building sector consumes the largest proportion of site energy used in Germany, and the lion’s share—about 75%—of this use is attributable to space heating. Consequently this share has to be reduced radically for overall energy consumption and carbon dioxide (CO2) emissions to decline. Existing buildings are of particular importance. At present, older buildings use on average 225 kilowatt-hours per square meter (kWh/m2) (71,325 British thermal units per square foot (Btu/ft2)) annually—or 3 times the energy required to heat a new building. Yet despite rising energy prices, retrofit projects are still not fully exploiting potential energy savings. Currently, over half of the potential savings that are economically feasible remain untapped after a renovation.